The main light emitting mode for OLED devices in AM-OLED (active matrix-organic light-emitting display) display is emitting light from the cathode side; as shown in FIG. 1, an anode 040 and a cathode 020 are respectively located on both sides of a functional layer 030. When an electric field more than a certain threshold is applied on the anode 040 and the cathode 020, holes and electrons enter the light emitting layer of the functional layer 030 respectively from the anode 040 and cathode 020; then the radiative recombination causes luminescence; as shown with the arrow in the drawing, the light is emitted from the cathode 020 side, so as to realize display.
However, the transmittance of the cathode is relatively low since it is typically made of metals and/or alloy materials with a low work function; in order to reduce the influence of the cathode on the overall luminous efficiency of the OLED device, the thickness of the cathode should be smaller. However, when the thickness of the cathode is small, the surface resistance Rs (Rs=ρ/t, ρ is the resistivity, t is the thickness) will increase significantly, resulting in a high driving voltage of the OLED device, increasing the energy consumption.